Pump



July 8, 1947. G, w, HARDY 2,423,701

PUMP

Filed Jan. 1', 194s In@ I.

HNVENTQR 60mm W. Hmm

AQRNEY @atented July comme vv. nerdy, umile, ohm, assigner to 'rile Marquette Metal Products Company, Cleveland, (Ehio, a corporation of @lilo Application Jan l f if 7 Sie.

i, ists, serial No. 570,825

(ci. ics-iro but have been subject to certain disadvantages..

This has `been particularly true in recent years and in the aircraft held, Pumps ci this class es commonly used have not made emclent use ci the driving power applied to the pump to re ciprocate the pistons. This lack of eihciency is present in that known type of pump embodying vone or more sets of opposed pistons driven by an eccentric or single crank which aords only' one stroke per piston per revolution. Such pumps may have several pistons among which the peals driving power is divided at one time but this construction results in a proportionate increase in weight and driving power as the capacity is increased.

The present. pump embodies a simplified construction by which a maximum volumeoi fluid is pumped with a construction of minimum weight; thus providing a compact Aunit for aircraft use where weight and volume are at a premium. A single driving c with several loir/es engages como histoirs in succession to ei lect the pumping action. The pistons and lobes are so formed and spaced with respect to each other to utilize most emciently the pump driving force. The peak driving force applied to the cam is applied to only one piston at a time but to that piston several times per cam revolution.

herefore, it has been the chief object of this invention to provide such a pump mechanism in which the peak driving thrust o the rotating cam or driver is applied to only one piston at a time but to that piston more than once per drive shaft revolution. A further object of the in= ventiogn has been to attain maximum volume and uniiormityin flow of the pumped iuid with a minimum number of pump pistons. Still another object has been to provide a simplified pump piston and valve construction.

Other objects o the invention will become apparent lrom study of this specilcation and the accompanying drawing. The novel features of the invention are summarized in the claims.

Referring now to the drawings:

Fig. l. is a transverse section normal to the cam axis through a pump embodying my inven tion;

Fig. 2 is a section in a plane similar to Fig. i showing a modification employing three pump pistons, and

Fig. 3 is a similar section illustre-.ting lication with four pistons.

In Fig. 1 there is shown a hollour pump -s provided with a cylindrical bore i cam il Journalled in end caps (not shown) for rotatie in either direction in the bore of the case. the illustrations the cam is shown. as rota clockwise. The end caps are secured in pier bolts threadingly received in holes in th case. A. shaft id is driven from a suitable source to rotate the cam.

A pair of opposed cylinders it and i@ are for with their side walls integral with the ce. though if desired they may be termed sepa and bolted or otherwise secured thereto. cylinders are in alignment with each ot their common axis is normal to and `in the cam axis of rotation. Each cylindre-i larged its end and tapped to receive a can iii.

The .laid to be pumped by each piston l1"? initieel to each cylinder by an inlet port cylinder side wall and expelled by an cutie-ij discharge port il formed in a respective end Pump pistons iii are carried in each cy and pump as they are forced outwardly by e of the cam t. Each piston is :formed i. ward with a semi-spherical sur insure uniform sliding engagement with t lobes irrespective of the rotated position er piston in its cylinder. lli desired a oail or may be carried by the piston to form an friction bearing with the cam face. if is used the piston is restrained in any manner against rotation in its cylinder.

Three symmetrical lobes 2@ are formed o cam as shown. The peripheral suraces lobe are alike, symmetrical involute, as si and are formed to smoothly convert the i applied by rotation of the cam to pis reciprocate them. There is no appreciable at the peaks of the cams since it is clesirahl have the suction strokes start as soon es sible after completion of the pressure or om strokes. The advantages in the use of the metrical involute shape ci cam lobe the pistons move at a uniform speed both out if the cam is rotated at a uniform sV the pump is reversible; the gradual return i the pistons on the suction strokes avoids hence noisy operation and the tendency to ste. which often characterizes the 'use oi sprinef turned pistons when the return movement is checked by the cam. Such conditions obtain the cam has a sudden drop-oi? or steep slope yond the apex. It will be apparent that each lobe causes a power stroke of each piston once a revolution. Thus with the construction shown in Fig. 1 six power or pumping strokes take place for each cam revolution although there are only two pistons.

. The spacing of the cam lobes and pistons is such that the peak driving force of the shaft is only applied to one piston at a time, insuring that the maximum po'wer input is most eillclently used to move the pistons to pump fluid. Thus a minimum of driving force is applied to a single piston several times per cam revolution with the result that the input from the prime mover is most eiliciently used and more even ilow of the pumped fluid attained.

As each piston forces fluid through its outlet the fluid pressure opens a spring loaded ball check valve 22 formed in an end cap l5 (see right side Fig. 1). At the end of each pumping stroke the lobe 20 applying the force passes the piston end I9 which is then returned inwardly by a coil spring 24 seated at one end in the end cap and at the other end in a recess in the piston. The resistance to opening offered by the spring may be varied by adjusting the screw 23.

A vacuum tends to be established between the piston and the end cap as the piston starts its return stroke because the check valve closes to prevent fluid from ilowing from the outlet back into the cylinder (see left side Fig. 1). To relieve this the fit between the piston and cylinder side wall is of a calculated clearance to allow iiuid from the inlet to be drawn ahead of the piston on its return stroke. This is an advantage as it effectively results in an increase in pressure in the iiuid inlet line at the time the cylinder is charged. Leakage of fluid past the piston into the bore B is prevented by a linear seal 26 carried by the piston.

In certain cases it is desired to employ more than two pistons and this may be accomplished by the modications of Figs. 2 and 3. In these figures all parts are labelled as in Fig. 1 except that the case is designated 5a in Fig. 2 and 5b in Fig. 3. The case of Fig. 2 has been formed to receive three cylinders and the case of Fig. 3 has :been formed to receive four cylinders.v Except for the cases and thus the number of cylinders, all parts of these two modifications are identical with corresponding parts of Fig. 1 and these modiiications make use of the power input in the same leiiicient manner.

if peak load is being applied at the right hand' piston the left hand piston is being returned by its spring. The top piston is fully returned and the lower piston has just reached the end of lts pumping stroke, If other positions of the cam of piston cylinders rigid with said case and in communication therewith, a pump piston in each cylinder and a rotatable cam member with a plurality of equally spaced lobes or uniform shape to drive said pistons through apumping stroke, said pistons and said cam lobes having such position and conguration that the cam applies peak driving force to only one piston at a time.

2. A pump comprising a hollow case, a plurality of piston cylinders rigid with said case and in communication therewith, an inlet port in each cylinder adjacent said case, an outlet port in each cylinder, a check valve to prevent travel of fluid from each outlet to each cylinder, a. pump piston in each cylinder, and a rotatable cam member with a plurality of equally spaced lobes of uniform shape to drive said pistons through a pumping stroke, said pistons and said cam lobes having such position and conilguration that the cam applies peak driving force to only one piston at a time.

3. A pump comprising a hollow case, a plurality of piston cylinders rigid with said case and in communication therewith, an inlet port in each cylinder adjacent said case, an` outlet port in each cylinder. a check valve to prevent travel of fluid from each outlet to each cylinder, a pump are assumed for each figure it will be seen that maximum or peak driving force is applied' to only one piston at a time. It is applied to each piston several times a revolution and thus makes most eiliclent use of the driver input to the pump.

I claim:

1. A pump comprising a hollow case, a plurality piston in each cylinder with suillcient clearance between the piston and cylinder side wall to permit withdrawal of said piston from the outlet port without creating a vacuum adjacent said outlet port, and a rotatable cam member with a plurality of equally spaced lobes of uniform shape to drive said pistons through a pumping stroke, said pistons and said cam lobes having such position and configuration that the cam applies peak driving force to only one piston at a time.

4. A pump comprising a hollow case, two piston cylinders rigid with said case and in communication therewith, a pump piston in each cylinder, resilient means to urge each piston in one direction toward the center of said case and a rotatable cam member with a plurality of lobes to drive said pistons through a pumping stroke against said resilient means, said pistons and said cam lobes having such position and configuration that the cam drives only one piston at a time through a pumping stroke and simultaneously allows return of the other piston by its associated resilient means.

5. A .pump comprising a hollow case, a pair of opposed piston cylinders rigid with said case and in communication therewith, an inlet port and an outlet port in each cylinder. a check valve to prevent return travel of fluid from each outlet to eac-h cylinder, a pump piston in each cylinder with sufficient clearance between the piston and cylinder sidewall to permit withdrawal of said piston from the outlet port without creating a vacuum adjacent said outlet port, and rotatable means operable to drive only one of said pistons at a time through a pumping stroke.

6. A pump comprising a hollow case, a pair of opposed piston cylinders secured to said case and in communication therewith, an inlet port in each cylinder adjacent said case, an outlet port in each cylinder, a check valve to prevent return travel of fluid from each outlet to each cylinder, a pump piston in each cylinder with sufiicient clearance between the piston and cylinder side wall to permit withdrawal of s aid piston from the outlet port without creating a vacuum adjacent said outlet port, resilient means to urge each piston in a return direction toward said case and a cam member with a plurality of lobes in 6 said case and rotatable in either direction therein uniform rate and the cam applies driving force to to drive said pistons through a Pumping stroke only one of said pistons at a time. against said resilient means, said pistons and said cam lobes having such position and con- GORDON W. HARDY- guration that the cam drives only one piston 5 at a time through a pumping stroke and simul- REFERENCES CITED taneusly allows return of' the other pistn by its The following references are of record in the associated resilient means. t file of this patent. 7. A pump comprising a, hollow case, two oppositely disposed-piston cylinders rigid with the l0 UNITED STATES PATENTS case and in communication therewith, a pump piston in each cylinder and a. rotatable cam mem- Nugego Plaame se tngtelgos axis intersecting the cylinder axes and p 1 heron an 1,309,257 Martens July a, 1919 Bidwell July 26, 1938 Beeh Oct. 22, 1940 having three lobes of involute form operative on 2 124 604 the opposed pistons alternately during rotation 1;, 2219002 of the cam whereby the pistons are moved at a 

